This article will explain the differences between counting days and nights. The Count setting is used to specify if days or nights are used as the basis of determining the duration of a booking.
In the app, you can locate the setting in the Date Range section of the product page just after the Duration settings.
Days- Counts per day that passes.
ie. If you book January 1st for 1 Day, the booking runs from January 1st to January 1st. (Morning of January 1st to evening of January 1st.)
Nights- Counts per night that passes.
ie. If you book January 1st for 1 Night, the booking runs from January 1st to January 2nd. (Evening of January 1st to the morning of January 2nd).
Either scenario would still allow January 2nd to be available for booking as long as no lead or lag time has been applied.